16 research outputs found
B\"acklund Transformation for the BC-Type Toda Lattice
We study an integrable case of n-particle Toda lattice: open chain with
boundary terms containing 4 parameters. For this model we construct a
B\"acklund transformation and prove its basic properties: canonicity,
commutativity and spectrality. The B\"acklund transformation can be also viewed
as a discretized time dynamics. Two Lax matrices are used: of order 2 and of
order 2n+2, which are mutually dual, sharing the same spectral curve.Comment: This is a contribution to the Vadim Kuznetsov Memorial Issue on
Integrable Systems and Related Topics, published in SIGMA (Symmetry,
Integrability and Geometry: Methods and Applications) at
http://www.emis.de/journals/SIGMA
Eigenproblem for Jacobi matrices: hypergeometric series solution
We study the perturbative power-series expansions of the eigenvalues and
eigenvectors of a general tridiagonal (Jacobi) matrix of dimension d.
The(small) expansion parameters are being the entries of the two diagonals of
length d-1 sandwiching the principal diagonal, which gives the unperturbed
spectrum.
The solution is found explicitly in terms of multivariable (Horn-type)
hypergeometric series of 3d-5 variables in the generic case, or 2d-3 variables
for the eigenvalue growing from a corner matrix element. To derive the result,
we first rewrite the spectral problem for a Jacobi matrix as an equivalent
system of cubic equations, which are then resolved by the application of the
multivariable Lagrange inversion formula. The corresponding Jacobi determinant
is calculated explicitly. Explicit formulae are also found for any monomial
composed of eigenvector's components.Comment: Latex, 20 pages; v2: corrected typos, added section with example
Q-operator and factorised separation chain for Jack polynomials
Applying Baxter's method of the Q-operator to the set of Sekiguchi's
commuting partial differential operators we show that Jack polynomials
P(x_1,...,x_n) are eigenfunctions of a one-parameter family of integral
operators Q_z. The operators Q_z are expressed in terms of the
Dirichlet-Liouville n-dimensional beta integral. From a composition of n
operators Q_{z_k} we construct an integral operator S_n factorising Jack
polynomials into products of hypergeometric polynomials of one variable. The
operator S_n admits a factorisation described in terms of restricted Jack
polynomials P(x_1,...,x_k,1,...,1). Using the operator Q_z for z=0 we give a
simple derivation of a previously known integral representation for Jack
polynomials.Comment: 26 page
Cherednik operators and Ruijsenaars-Schneider model at infinity
Heckman introduced N operators on the space of polynomials in N variables, such that these operators form a covariant set relative to permutations of the operators and variables, and such that Jack symmetric polynomials are eigenfunctions of the power sums of these operators. We introduce the analogues of these N operators for Macdonald symmetric polynomials, by using Cherednik operators. The latter operators pairwise commute, and Macdonald polynomials are eigenfunctions of their power sums.We compute the limits of our operators at N→∞. These limits yield a Lax operator for Macdonald symmetric functions
Quantization of the Kadomtsev–Petviashvili equation
We propose a quantization of the Kadomtsev–Petviashvili equation on a cylinder equivalent to an infinite system of nonrelativistic one-dimensional bosons with the masses m = 1, 2,.. The Hamiltonian is Galilei-invariant and includes the split and merge termsΨm1†Ψm2†Ψm1+m2andΨm1+m2†Ψm1Ψm2for all combinations of particles with masses m 1, m 2, and m 1 + m 2for a special choice of coupling constants. We construct the Bethe eigenfunctions for the model and verify the consistency of the coordinate Bethe ansatz and hence the quantum integrability of the model up to the mass M=8 sector
Combinatorics of generalized Bethe equations
A generalization of the Bethe ansatz equations is studied, where a scalar
two-particle S-matrix has several zeroes and poles in the complex plane, as
opposed to the ordinary single pole/zero case. For the repulsive case (no
complex roots), the main result is the enumeration of all distinct solutions to
the Bethe equations in terms of the Fuss-Catalan numbers. Two new combinatorial
interpretations of the Fuss-Catalan and related numbers are obtained. On the
one hand, they count regular orbits of the permutation group in certain factor
modules over Z^M, and on the other hand, they count integer points in certain
M-dimensional polytopes
Lax operator for Macdonald symmetric functions
Using the Lax operator formalism, we construct a family of pairwise commuting operators such that the Macdonald symmetric functions of infinitely many variables and of two parameters q, t are their eigenfunctions. We express our operators in terms of the Hall-Littlewood symmetric functions of the variables and of the parameter t corresponding to the partitions with one part only. Our expression is based on the notion of Baker-Akhiezer function